[Mike Fowke]

There is a "ridge" the ramp where the edge of the roller rides. I can barely catch a finger nail on it. It's smooth on the nose and base. The lifter and bore seem fine, and I only found this on one lobe.

Is this anything to worry about?

Kauffman 236/242 - Johnson Short Travel lifters

[77 TRASHCAN]

Pictures???

[25stevem]

Sounds like that lifter bore has a taper at its top such that when the lifter is on the base of the cam the lifter is no longer perpendicular to the cam.

[Mike Fowke]

Originally Posted by 25stevem

Sounds like that lifter bore has a taper at its top such that when the lifter is on the base of the cam the lifter is no longer perpendicular to the cam.

That makes sense. I don't see a reason to replace anything at this point.

I'll try to take a picture, but I don't think it will show much.

[tom s]

Make REAL sure none needle bearings are wearing away,happened to me some years ago,caught it just in time.Tom

[chuckies76ta]

Originally Posted by Mike Fowke

There is a "ridge" the ramp where the edge of the roller rides. I can barely catch a finger nail on it. It's smooth on the nose and base. The lifter and bore seem fine, and I only found this on one lobe.

Is this anything to worry about?

Kauffman 236/242 - Johnson Short Travel lifters

I'm curious, Do you know what springs you are using and close and open pressures? How much lift, and what rocker ratio? I ran those Johnson short travel lifters in a 400. Made 550 hp. Sold engine years ago and still running strong with no issues. Guy just went a round trip of 2000 miles no issues. I remember the rep at Johnson telling me to set lash was very specific. Not you quarter turn or half turn after preload. I actually measured with a set of calipers.
Thanks

[Mike Fowke]

Originally Posted by tom s

Make REAL sure none needle bearings are wearing away,happened to me some years ago,caught it just in time.Tom

Thanks Tom. The roller feels consistent with the others, and it looks good.

[25stevem]

How do the ware marks look on the side’s of the body of that lifter as compared to others?

It could also be that the parent steel that cam is made from just was not tempered quite as much right there .

[Mike Fowke]

Originally Posted by chuckies76ta

I'm curious, Do you know what springs you are using and close and open pressures? How much lift, and what rocker ratio? I ran those Johnson short travel lifters in a 400. Made 550 hp. Sold engine years ago and still running strong with no issues. Guy just went a round trip of 2000 miles no issues. I remember the rep at Johnson telling me to set lash was very specific. Not you quarter turn or half turn after preload. I actually measured with a set of calipers.
Thanks

I don't know what the spring rates are. I bought the heads complete from Kauffman. The cam lift is advertised at .360 lift, and the rockers are 1.65.

So, to make a short story long, I'm still chasing a problem at WOT that I've posted about before. Under load, it backfires or breaks up. I'm pretty confident that it isn't the ignition system or fuel. I'll post my tests in another reply. I ran a compression test, and watched the rocker's movement on the starter. All looked good. Since the problem is at WOT, I didn't expect to find any problems. I ran out of ideas and pulled the rockers and pushrods. The rockers are fine, and none of the rods are bent. So, I yanked the lifters. That's when I noticed the wear on the lobe. I also found a very small piece of debris in the cup of one of the lifters (hard, non-metallic). I took it apart and cleaned it. The others seem fine, but I'm going to soak them in mineral spirits for good measure.

Back to the springs. The heads arrived from Kauffman with valve cuts that weren't concentric to the seats. A local shop re-cut the valves, and all was good for a while. I don't think this is related, but I wonder if one of the springs is giving up. Since I'm this far in, I might as well have them measured. Thoughts?

[25stevem]

I would pull all the springs off and check them.

I was helping out a racing buddy with his Mopar that had just such a issue that he was dealing with at 7800 rpm for two seasons.
We ultimately found the very top coil of two of his inner springs had busted.
This produced the result of some 35 less psi of spring pressure then what he thought he had and misfire above 7400 rpm , and like you only under load.

I am not saying you have busted springs, but weak springs would be the first place I would look!

With the size valves we are taking about here and the added weight of roller lifters and thicker wall push rods I would want to see 150 to 155 psi on the seat with new springs which after a few high rpm runs will drop off to 140 to 145.

If the springs check out then it’s time to look at the fuel supply and what you have for pressure at full throttle.
What does your system consist of, stock size steel lines running up from the tank?

Stock size fuel pick up in the tank?

Only using one side of a two port fuel regulator is a big restriction as is one of those cheap Holley Blue regulators in and of themselves!

A ignition miss will not most times make for engine damage, but high speed lean out to the point of making for a Miss sure will.

[Mike Fowke]

Ignition system: MSD Ready to Run, Blaster Coil, NKG plugs, and Taylor wires. I replaced the coil and plugs. Swapped the wires for a known good set. Swapped the MSD for the original, worn out, HEI. None of this fixed the problem at WOT.

Fuel: Qjet, .044 secondary rods, 73 jets, .145 inlet, sealed vent. Aeromotive Returnless Phantom in tank pump, Rick's tank (baffled), -8AN fuel line, Holley regulator (12-843). Fuel pressure is steady at WOT when the engine "breaks up". No change with fuel pressure between 5.5 and 8. Cliff says the carb recipe should be a tad rich. To be sure the engine wasn't gong lean at WOT, I removed the secondary rods, but it still broke up.

Engine: 473, Kauffman 300 cfm aluminum heads, Kauffman 236/242 hydraulic roller, '72 stock intake ported to match heads, open plenum. Doug's 1 3/4" headers, 3" exhaust w/ H pipe.

[Mike Fowke]

Steve - Appreciate the advice. I'll pull the springs. You treed me by four minuets. See my last post about fuel pressure.

[mchell]

Originally Posted by Mike Fowke

Ignition system: MSD Ready to Run, Blaster Coil, NKG plugs, and Taylor wires. I replaced the coil and plugs. Swapped the wires for a known good set. Swapped the MSD for the original, worn out, HEI. None of this fixed the problem at WOT.

Fuel: Qjet, .044 secondary rods, 73 jets, .145 inlet, sealed vent. Aeromotive Returnless Phantom in tank pump, Rick's tank (baffled), -8AN fuel line, Holley regulator (12-843). Fuel pressure is steady at WOT when the engine "breaks up". No change with fuel pressure between 5.5 and 8. Cliff says the carb recipe should be a tad rich. To be sure the engine wasn't gong lean at WOT, I removed the secondary rods, but it still broke up.

Engine: 473, Kauffman 300 cfm aluminum heads, Kauffman 236/242 hydraulic roller, '72 stock intake ported to match heads, open plenum. Doug's 1 3/4" headers, 3" exhaust w/ H pipe.

Pull the top of the carb off and make sure a fuel pick up tube hasn’t dropped….. did you try a different carb for giggles?

[Mike Fowke]

Originally Posted by mchell

Pull the top of the carb off and make sure a fuel pick up tube hasn’t dropped….. did you try a different carb for giggles?

I've had the carb apart a good bit lately, and the pickup tubes are good. I've also thought it would be nice to try another carb, but I don't have access to anything that would be close to this one.

[Mike Fowke]

Originally Posted by 25stevem

How do the ware marks look on the side’s of the body of that lifter as compared to others?

It could also be that the parent steel that cam is made from just was not tempered quite as much right there .

The wear marks are consistent. At this point, I'm not too worried about the cam. I'll check it in another 5k miles or so and see if it's any worse. It's a weekend warrior and once a month autocross car.

[mchell]

Originally Posted by Mike Fowke

I've had the carb apart a good bit lately, and the pickup tubes are good. I've also thought it would be nice to try another carb, but I don't have access to anything that would be close to this one.

10/4

Reading your post again…. Noticed you mentioned backfire. Tough one as it could be going lean (carb) ……or ignition. Sounds Ike you ruled out valve train and cam.

A few things you probably looked at:
When’s the last time you pulled the dist. and checked the dist. gear? Try a spare dizzy? Plugs look OK? Timing coming in good, not advancing to much at wot? Do you limit dist advance?

[Mike Fowke]

Originally Posted by mchell

10/4

Reading your post again…. Noticed you mentioned backfire. Tough one as it could be going lean (carb) ……or ignition. Sounds Ike you ruled out valve train and cam.

A few things you probably looked at:
When’s the last time you pulled the dist. and checked the dist. gear? Try a spare dizzy? Plugs look OK? Timing coming in good, not advancing to much at wot? Do you limit dist advance?

See post 11. I think I've ruled out ignition and fuel. I didn't consider the distributor gear, but I used the same one to test the HEI. I think I would have noticed any wear. Timing is 12 initial, 30 total (recently verified). I think the MSD advance stop bushing limits total.

Tomorrow I'm going to call the machinist who fixed the heads and explain the problem. I'm sure he'll measure the springs for me, and he may want to see the heads. I'll go from there.

Thoughts and suggestions are still welcome, and I appreciate the feedback.

[chuckies76ta]

Mike, get a Carb like an 850 Holly or Quickfuel and try it. The fuel pressure should not be over 7 psi. I like 6.5 psi. It's either electrical or fuel delivery. Change one thing at a time. Carb, MSD distrubutor, coil, MSD box. The only other thing to consider is it's possible your loosing 12 volts to the distributor. If your running a MSD box, it maybe the rev limiter chip or where ever it's set at. Set to highest setting for testing. Don't the new Ready to run Distributors have a rev limiter incorporated in them?

What rpm does it start breaking up at.

[Mike Fowke]

Originally Posted by chuckies76ta

Mike, get a Carb like an 850 Holly or Quickfuel and try it. The fuel pressure should not be over 7 psi. I like 6.5 psi. It's either electrical or fuel delivery. Change one thing at a time. Carb, MSD distrubutor, coil, MSD box. The only other thing to consider is it's possible your loosing 12 volts to the distributor. If your running a MSD box, it maybe the rev limiter chip or where ever it's set at. Set to highest setting for testing. Don't the new Ready to run Distributors have a rev limiter incorporated in them?

What rpm does it start breaking up at.

I should have paid more attention to exactly when it starts to break up. I'm guessing between 4,500 and 5,000. The Ready to Run does have a rev limiter, and I have it set to about 6,200. When I initially set it up, I had it too low. The problem I'm experiencing isn't like hitting the limiter. I'm getting a hard, rapid misfire. The rev limiter just cuts the spark, and the car slows down with no drama.

I've been through the fuel and ignition system. I verified that fuel pressure is consistent when it breaks up, and replaced the coil, plugs, wires. I also put my old HEI back in which doesn't have a limiter. Same results.. I haven't thought about a voltage issue though. Need to think about that.

[68WarDog]

Originally Posted by 25stevem

I would pull all the springs off and check them.

Interesting Steve, about 14/15 years ago I ran a solid roller engine that had a high rpm misfire like the op. After going through carb, replacing the pv. And spark plug wires and distributor cap and rotor. Everything checked out. #4 and IIRC #7 exhaust valve springs were broken, even though the lash remained on spot. After replacing all the springs, the misfire went away.